Lacking meaning, to be blunt (9)
I believe the answer is:
pointless
'blunt' is the definition.
(similar in meaning)
'lacking meaning to be' is the wordplay.
'lacking meaning' becomes 'less' (I am not sure about this - if you are sure you should believe this answer much more).
'to' means one lot of letters go next to another (I've seen this in other clues).
'be' becomes 'point' (pointing is a kind of being).
'less' put after 'point' is 'POINTLESS'.
Can you help me to learn more?
(Other definitions for pointless that I've seen before include "Ineffectual" , "Single-track railway might be so" , "missing a target" , "having scored zero" , "Quite vain" .)